1. Field of the Invention
The present invention deals with a human powered aquatic craft. It has to do with an aquatic vessel capable of moving over the water at very high speeds due to a very narrow and long hull that is driven by human leg power applied on pedals that transmit it to a propeller placed well forward of the hull, at the back of a free turning keel. Such directionable keel and propeller, placed near the hull bow, give enough turning power to redirect the vessel and to maintain the crafts balance, eliminating the need of a rudder and many associated parts, and making it natural and logical to use by any ground bike rider.
2. Description of the Related Art
Most all pedal driven watercraft up to recent dates are heavy and slow. The reason is that the wide flat bottom is needed to stay upright. This necessitates using a large wetted surface which slows the vessel, restricting the usage of pedal boats to easy going recreational activities in flat, calm, close water areas. To overcome this, catamaran type pedal driven vessels have been developed. The two pontoons give enough width for stability with lower wetting surface and therefore somewhat higher speeds, but still lower speeds as compared to a single narrow hull. Both types of vessels are hard to handle in choppy waters in bad weather because they tend to capsize with medium to large swells.
Recently a canard balanced water bicycle, consisting of: narrow mono-hull, bicycle frame, pedal driven back propeller, direction stern rudder and movable canard under the hull at about mid-ship was introduced.
This water bicycle turned out to be the fastest long range human powered vehicle because of its long narrow hull. It can work on open water because of its round shaped hull and its balance with the underwater canard. Unfortunately it turned out to be too complex, too heavy, with many parts, hard to maintain, non user friendly and very expensive. This is so because it uses the deep moving canard for balance, a stern rudder activated by cables with brake levers on the handlebars, a gear system that moves a shaft that passes through the hull and a back stainless steel flexible support to keep the propeller and shaft in place.
Another disadvantage is the draft. The keel, the rudder and the propeller are so deep that it is impossible to move around shallow water or fishing nets, and make it unfeasible to land on shallow shores.
The biggest disadvantage though is the counteracting forces that the canard, or moving keel and the rudder create. When in motion, the canard being very close to the center of buoyancy and/or the center of mass, gives a strong restoring force when turned by a small angle. On the other hand, the rudder at the stern, when used to turn by means of the brake handles creates a tilting or falling force on the hull rider system. Therefore the rider must apply additional restoring force with the canard to compensate for the tilting force of the rudder when an-attempt to change course is made.
This unnatural behavior doesn't resemble that of making a turn with a ground bicycle and wastes useful energy, especially on races where optimum use of it is wanted. The energy loss comes from the drag the two foils create when one is turning while the other is keeping hull balance. This adds to the weird feeling of a seasoned cyclist that uses the brake handles to turn instead of stopping and the handlebar to stay vertical instead of turning.
Therefore, none of the prior boats have a system as simple and reliable as that of a ground bicycle to turn and keep balance, using only the handlebar, while at slow or fast motion.
In order to understand what is meant by bicycle-type, a little analysis of the ground forces is in order,
A ground bicycle (gb) rider, when at very low speed, like when waiting for the green light, usually stays upright by means of handlebar turnings from one side to the other and short pedal pushes.
Basically when balance is lost to one side, the handlebar is turned to the same side a long with slight pedal push and balance is restored by a short displacement of the bike towards the resultant direction of fall. Immediately the rider straightens up and prepares himself to react in the direction where balance gets lost again, until the green light turns on and he can speed up and profit from the wheels gyroscopic effect for easier balance. It is important to emphasize that primarily the balance comes from the slow motion dynamics explained before and the fast speed gyroscopic effect is only additional help.
Now let's look at the dynamics of this slow motion balance. FIGS. 1, 2 and 3 show the speed and force vectors acting on the rider.
In these figures the arrows are:
A is the forward momentum PA1 B is the falling trend PA1 C is the opposition of the ground to the tilted tire or the opposition of the water to the tilted keel. PA1 D is the rider forward momentum when the tire or keel is tilted PA1 E is the resultant motion due to falling trend B and forward trend D PA1 F is the restoring trend due to the canard action against the water PA1 G is the falling trend due to the rudder action against the water
FIG. 1 represents a ground bicycle. In 1a) the rider loses balance to the left. In 1b) he turns to the left. The ground presents an opposition to continue to go forward. The rider momentum (D) tends to continue in the forward direction (Newtons first law). The resultant rider's motion is towards the left and forward (E). On the other hand the easy direction for the front tire that is being pushed by the pedal power is towards the front left (E). In 1c) the rider reaches balance again. In 1d) the cycle starts again, but this time to the right side.
The stronger the fail seems, the bigger the handlebar turning in order to balance in the new direction the momentum forward trend with the gravity falling trend.
In the previous art, in FIG. 2a), the canard balanced water craft restores balance by turning the handlebar and therefore the canard 2b), and opposing resistance to the oncoming water on one side, creating an immediate restoring torque (F) as can be seen in FIG. 2b), with almost no directional or course change, since the canard stands very lose to the center of mass.
The bigger the canard tilting, the larger the restoring force.
The big disadvantage comes with the aft rudder as can be seen in FIG. 2b. Changing course creates a falling force (G) that tends to flip the hull. Extra canard compensation (F) is needed in order to avoid falling, increasing water drag. Another means to counteract the fall is to lean the body towards the opposite side of the turn, contrary to the behavior on a ground bicycle.
The bicycle-type marine vessel is shown in FIG. 3. The resemblance to a ground bicycle is apparent. The rider turns the handlebar when balance is lost and the keel-propeller system powers the boat in the new direction. The water opposes the forward motion (C), the easy direction is (E), which is also the resultant direction (E) of fall trend (B) and forward momentum trend (D). The rider reaches balance 3c) and the cycle starts again 3d).
If the rider wants to make a turn, he leans the body towards the turning side, and tilts the forward keel-propeller towards the new direction and balance is restored when the hull turns just like in a ground bicycle.